1. Technical Field
The present invention relates to a belt tracking system, a multi-roller assembly and an image forming apparatus employing the same, and more particularly, to a belt tracking system for controlling the lateral position of a movable belt entrained about a plurality of rollers, and a multi-roller assembly and an image forming apparatus employing the belt tracking system.
2. Background Art
Image forming apparatuses employ various types of movable imaging belts, such as an intermediate transfer belt, a media conveyance belt, and a fixing belt, each of which is entrained about a plurality of generally parallel rollers for moving in a trans-axial direction perpendicular to an axial direction in which the rollers extend parallel to each other.
One problem associated with a multi-roller belt support assembly is that the movable belt occasionally walks or moves laterally in the axial direction due to a lack of parallel alignment between the belt support rollers, which results, for example, from wear and tear of equipment used to rotate the belt support rollers. Such lateral displacement of the belt, if not corrected, would cause breakage or failure of the imaging process where the belt reaches the axial end of the roller and eventually slips off the belt support assembly.
To address this problem, several techniques have been proposed which employ a belt tracking system connected to an axial end of the belt support roller to control the lateral position of the movable belt.
For example, there is known a belt tracking system in which a movable belt is entrained around a steering roller. The steering roller is equipped with a pair of rotary, slidable members each rotatably mounted to an axial end of the roller to define an inclined, conical interfacial surface therealong to slidably contact a stationary member. The system is designed to correct lateral displacement of the belt by tilting the steering roller as the slidable member slides against the stationary member along the inclined interfacial surface where the belt moves laterally outward to the axial end of the roller.
The inventors have recognized that, although generally successful, the belt tracking system that employs sliding contact between the slidable member and the stationary member for tilting the steering roller can fail to work properly where the slidable member occasionally separates from the stationary member due to an external force, such as, for example, tension in the movable belt stretched around the belt supporting roller.